Thin-films containing organic materials with electron transport or hole transport properties have potential applications in organic thin-film devices including organic thin-film transistors, organic solar cells, optical sensors, organic electroluminescent devices and the like, but because organic n-type semiconductors (that exhibit electron transport properties) are harder to obtain than organic p-type semiconductors (that exhibit hole transport properties), a great deal of research is being expended for development of organic n-type semiconductors.
Because fluoroalkyl group-introduced π-conjugated compounds have increased electron acceptability, such compounds can potentially be developed into electron transport materials such as organic n-type semiconductors. Much research has therefore been devoted in recent years to compounds obtained by introducing fluoroalkyl groups into thiophene rings, and particularly oligothiophene rings (see Patent documents 1-4).
On the other hand, development of oligothiophenes and polythiophenes having bithiophene-crosslinked structures is also being pursued with the goal of improving twist in the molecular structure (see Non-patent documents 1, 2 and Patent document 5).
(Patent document 1) U.S. Patent Application Publication No. 2004/186266
(Patent document 2) U.S. Patent Application Publication No. 2004/183068
(Patent document 3) International Patent Publication No. W02003/010778
(Patent document 4) European Patent Application Publication No. 1279689
(Patent document 5) Japanese Unexamined Patent Publication No. 2004-339516
(Non-patent document 1) Paolo Coppo et al., J. Mat. Commun. 2002, 12(9), 2597.
(Non-patent document 2) Paolo Coppo et al., Chem. Commun. 2003, 2548.